The field of the invention pertains to crossbows and crossbow trigger mechanisms. The invention relates more particularly to an anti-dry fire mechanism for crossbows, wherein an arrow contacting surface operates a hook-type catch to engage and prevent operation of a trigger mechanism.
Various types of trigger mechanisms have been specifically developed for use in crossbows. Many, if not most, of these crossbow trigger mechanisms are designed with built-in safety mechanisms which prevent accidental discharge of an arrow. However, these conventional safety mechanisms are typically not designed for preventing the release of a cocked but unloaded bowstring, i.e. when an arrow is not positioned for discharge. This situation, commonly known as "dry fire", can cause damage to the crossbow or be potentially hazardous to the user. In an effort to prevent the occurrence of dry fire situations, various dry fire prevention devices have been developed for crossbows which disable operation of the crossbow trigger mechanism while an arrow is not positioned to be discharged.
For example, in U.S. Pat. No. 5,085,200 a self-actuating, dry-fire prevention safety device for a crossbow is shown having a stop block 30 which pivotally operates to block forward movement of a safety assembly block plate 22 when an arrow is not positioned to be discharged. It does so by abutting a blocking portion 34 of the stop block 30 against a rounded operating pin 24 of the safety assembly block plate 22. The disadvantage of this arrangement is the limited efficacy and unreliability of a blocking impedance as opposed to impedance by catch-engagement. While exact alignment of the blocking component 34 with the operating pin 24 would effectively prevent dry fire (FIG. 5), the slightest variation in pivot angle of the stop block 30 may cause the blocking engagement to slip and thereby enable dry fire.
And in U.S. Pat. No. 5,598,829 a crossbow dry fire prevention device is shown having a string catch member with an arrow contacting surface which cause the string catch member to be moved out of the string catching position when an arrow is placed in the firing position. When the bowstring is cocked but an arrow is not in place, the string catch member is urged into the release path of the bowstring. In this manner, the string catch member functions to catch the inadvertently released bowstring to prevent dry fire. However, this arrangement does not operate to inhibit operation of the trigger mechanism. Notwithstanding the absence of an arrow, actuation of the trigger mechanism will release the cocked bowstring from the sear, only to be caught by the string catching member.
Similar to the 839 patent, a crossbow is shown in U.S. Pat. No. 5,884,614 also having a dry fire prevention mechanism which operates to block the release passage of a bowstring when an arrow is not in place. In particular, a safety latch positioned above the release passage is urged downward into the release passage by means of a safety latch spring. This arrangement, however, also does not inhibit operation of the trigger mechanism. While inadvertent release of the unloaded bowstring will not dry fire, the bowstring must be cocked again and reset onto the sear before successful operation may take place.
In summary, it is therefore desirable to provide a dry fire prevention safety mechanism for use on crossbows which not only blocks movement of the trigger mechanism, but directly catches a part of the trigger mechanism to prevent operation of the crossbow trigger mechanism when no arrow is positioned for discharge. Moreover, a dry fire prevention mechanism having a minimal number of moving parts, e.g. a single moving arm, would provide simplified operation, as well as reduce manufacturing costs compared to complex, multi-link dry fire prevention safety systems.